1. Technical Field
The present invention relates to image reading technology.
2. Related Art
There is an image reading apparatus such as a scanner apparatus that performs shading correction to prevent unevenness of the read image due to inhomogeneous brightness of the light source lamp, non-uniform sensitivity of the image reading device, or the like. Such an image reading apparatus, for example, before reading a document, scans a white reference surface and a black reference surface to obtain white reference data and black reference data to be used for shading correction (for example, JP-A-10-341342). The image reading apparatus produces a predetermined correction formula for each image reading device using the obtained white and black reference data. Next, the image reading apparatus performs shading correction to the read data of a document according to the correction formula.
By the way, there is an image reading apparatus performing shading correction that obtains the black reference data in a state where the light source lamp is turned off.
However, even an image reading apparatus which obtains the black reference data in a state where the light source is turned off, the light source is turned on when a document is actually read. When the light source is lit, noise is generated by a current, and crosstalk may occur in the output of the image reading device. Then streaky noise may appear in the read image data.